Heat transfer device

ABSTRACT

A heat transfer device includes a first member and a first and second heat transfer element. In the first heat transfer element, a first contact area that is a contact area between the first heat transfer element and the first member varies. In the second heat transfer element, a second contact area that is a contact area between the second heat transfer element and the first member varies. The first contact area is greater when magnitude of a first external force applied to the first member is smaller than a first threshold than when the magnitude of the first external force is equal to or greater than the first threshold. The second contact area is smaller when the magnitude of the first external force is smaller than the first threshold than when the magnitude of the first external force is equal to or greater than the first threshold.

BACKGROUND ART

Techniques using, for heat transfer, a solid material that exhibits thethermoelastic effect have been known.

For example, according to Patent Literature 1, a regenerator of acooling system includes a plurality of solid refrigerant materialscapable of exhibiting the thermoelastic effect. The cooling systemincludes a heat sink, a space to be refrigerated, and a regenerator. Thesolid refrigerant material is made of, for example, a shape-memory alloyand is shaped in the form of, for example, a wire.

According to Patent Literature 2, a lot of thermally straining materialsis used in each cooling/heating section of a cooling/heating moduleconfigured to cool and heat air. The thermally straining material ismade of, for example, a shape-memory alloy. The thermally strainingmaterial is formed in the shape of a wire extending vertically.

Patent Literature 3 describes a heat pump in which a shape-memory alloyis used. A belt is formed of the shape-memory alloy.

CITATION LIST Patent Literature

-   Patent Literature 1: JP 2012-220184 A-   Patent Literature 2: JP 2014-098552 A-   Patent Literature 3: JP S57-192761 A

SUMMARY OF INVENTION Technical Problem

In the techniques described in Patent Literatures 1 to 3, heat transferby thermal conduction is not expected to be performed by varying acontact area between a member including a solid material that exhibitsthe thermoelastic effect and a heat transfer element.

Therefore, the present disclosure provides a new heat transfer devicefor performing heat transfer by thermal conduction by varying a contactarea between a member including a solid material that exhibits thethermoelastic effect and a heat transfer element.

Solution to Problem

The present disclosure provides a heat transfer device including:

a first member including a first solid material that exhibits athermoelastic effect;

a first heat transfer element having a first contact area that variesand that is a contact area between the first heat transfer element andthe first member; and

a second heat transfer element having a second contact area that variesand that is a contact area between the second heat transfer element andthe first member, wherein

the first contact area is greater when magnitude of a first externalforce applied to the first member is smaller than a first thresholdbeing a threshold of an endothermic reaction and an exothermic reactionassociated with the thermoelastic effect of the first solid materialthan when the magnitude of the first external force is equal to orgreater than the first threshold, and

the second contact area is smaller when the magnitude of the firstexternal force is smaller than the first threshold than when themagnitude of the first external force is equal to or greater than thefirst threshold.

Advantageous Effects of Invention

Using the heat transfer device of the present disclosure, heat transferby thermal conduction can be performed by varying the contact areabetween the member including the solid material that exhibits thethermoelastic effect and each of the heat transfer elements.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view showing an example of a heat transferdevice of the present disclosure.

FIG. 2 is a cross-sectional view of the heat transfer device along aplane II shown in FIG. 1 .

FIG. 3 is a perspective view showing a first member of the heat transferdevice shown in FIG. 1 .

FIG. 4 is a perspective view showing an example of the heat transferdevice of the present disclosure.

FIG. 5 is an enlarged partial perspective view of the heat transferdevice shown in FIG. 4 .

FIG. 6 is a perspective view showing another example of the heattransfer device of the present disclosure.

FIG. 7 is a cross-sectional view of the heat transfer device shown inFIG. 6 along a plane VII.

FIG. 8 is a perspective view showing yet another example of the heattransfer device of the present disclosure.

FIG. 9 is a cross-sectional view of the heat transfer device along aplane IX shown in FIG. 8 .

FIG. 10 is another cross-sectional ie of the heat transfer device alongthe plane IX shown in FIG. 8 .

DESCRIPTION OF EMBODIMENTS

(Findings on which the Present Disclosure is Based)

It is conceivable that a heat transfer device is configured to mediateheat transport from a particular heat transfer element to another heattransfer element not by using, for example, fluorocarbon andhydrofluorocarbon but by using a solid material that exhibits thethermoelastic effect. Such a heat transfer device is advantageous interms of prevention of destruction of the ozone layer and prevention ofglobal warming. For example, heat of transition is generated by addingan external force to the solid material that exhibits the thermoelasticeffect and causing a phase transition. The value of the heat transferdevice can be enhanced by making a good use, in the heat transferdevice, of such absorption and release of heat associated with thethermoelastic effect. Moreover, properties of the heat transfer deviceis easily enhanced by bringing the solid material that exhibits thethermoelastic effect and a plurality of heat transfer elements intocontact with each other to cause heat transfer by thermal conduction.

The present inventors conducted intensive studies on a new heat transferdevice from such perspectives. Consequently, the present inventors havenewly found that a contact area between a solid material that exhibitsthe thermoelastic effect and each of a plurality of heat transferelements can be adjusted to be a desired condition by making use ofdeformation of the solid material resulting from adjustment of anexternal force for causing the solid material to absorb and releaseheat. On the basis of this new finding, the present inventors havedevised a heat transfer device of the present disclosure.

(Summary of One Aspect According to the Present Disclosure)

A heat transfer device of the present disclosure according to a firstaspect includes:

a first member including a first solid material that exhibits athermoelastic effect;

a first heat transfer element having a first contact area that variesand that is a contact area between the first heat transfer element andthe first member; and

a second heat transfer element having a second contact area that vanesand that is a contact area between the second heat transfer element andthe first member, wherein

the first contact area is greater when magnitude of a first externalforce applied to the first member is smaller than a first thresholdbeing a threshold of an endothermic reaction and an exothermic reactionassociated with the thermoelastic effect of the first solid materialthan when the magnitude of the first external force is equal to orgreater than the first threshold, and

the second contact area is smaller when the magnitude of the firstexternal force is smaller than the first threshold than when themagnitude of the first external force is equal to or greater than thefirst threshold.

According to the first aspect, the contact area between the first heattransfer element and the first member is greater when the magnitude ofthe first external force is smaller than the first threshold than whenthe magnitude of the first external force is equal to or greater thanthe first threshold. Therefore, heat easily transfers between the firstheat transfer element and the first member by thermal conduction whenthe magnitude of the first external force is smaller than the firstthreshold. On the other hand, the contact area between the second heattransfer element and the first member is greater when the magnitude ofthe first external force is equal to or greater than the first thresholdthan when the magnitude of the first external force is smaller than thefirst threshold.

Therefore, heat easily transfers between the second heat transferelement and the first member by thermal conduction when the magnitude ofthe first external force is equal to or greater than the firstthreshold. As described above, according to the first aspect, heattransfer by thermal conduction can be performed by varying the contactarea between the solid material that exhibits the thermoelastic effectand each of the plurality of heat transfer elements, and the solidmaterial that exhibits the thermoelastic effect can mediate heattransport between the first heat transfer element and the second heattransfer element. Additionally, the first external force can cause thefirst solid material to exhibit the thermoelastic effect, which makes itpossible to use, in the heat transfer device, absorption and release ofheat associated with the thermoelastic effect of the first solidmaterial.

According to a second aspect of the present disclosure, for example, inthe heat transfer device according to the first aspect, the firstcontact area may be greater than the second contact area when themagnitude of the first external force is smaller than the firstthreshold, and the first contact area may be equal to or smaller thanthe second contact area when the magnitude of the first external forceis equal to or greater than the first threshold. According to the secondaspect, heat transfer by thermal conduction is likely to be enhancedbetween the first heat transfer element and the first member when themagnitude of the first external force is smaller than the firstthreshold. Additionally, heat transfer by thermal conduction is likelyto be enhanced between the second heat transfer element and the firstmember when the magnitude of the first external force is equal to orgreater than the first threshold.

In a third aspect of the present disclosure, for example, in the heattransfer device according to the first aspect or the second aspect, thefirst solid material may be in a first phase when the magnitude of thefirst external force is smaller than the first threshold, and the firstsolid material may be in a second phase different from the first phasewhen the magnitude of the first external force is equal to or greaterthan the first threshold.

According to the third aspect, a phase transition of the first solidmaterial is induced by varying the magnitude of the first external forcewith respect to the first threshold, and thus the thermoelastic effectcan be exhibited.

According to a fourth aspect of the present disclosure, for example, inthe heat transfer device according to any one of the first aspect to thethird aspect, the first member may have a first inner perimeter and afirst outer perimeter, one of the first heat transfer element and thesecond heat transfer element may be disposed to face the first innerperimeter, and the other heat transfer element may be disposed to facethe first outer perimeter. According to the fourth aspect, the firstcontact area and the second contact area can be adjusted by adjustingthe first external force such that the first inner perimeter or thefirst outer perimeter of the first member is closer to the first heattransfer element or the second heat transfer element.

According to a fifth aspect of the present disclosure, for example, inthe heat transfer device according to the fourth aspect, the firstmember may be a first coil spring. According to the fifth aspect, thefirst contact area and the second contact area can be adjusted byadjusting the first external force around an axis of the first coilspring.

According to a sixth aspect of the present disclosure, for example, inthe heat transfer device according to the fifth aspect, a cross-sectionperpendicular to an axis of a linear element forming the first coilspring may include a pair of parallel line segments defining the firstinner perimeter and the first outer perimeter. According to the sixthaspect, the first contact area and the second contact area are easilyincreased.

In a seventh aspect of the present disclosure, for example, the heattransfer device according to any one of the first aspect to the sixthaspect may further include a first drive mechanism that cyclicallyincreases and decreases the first external force. According to theseventh aspect, the first external force can be cyclically increased anddecreased by the first drive mechanism.

In an eighth aspect of the present disclosure, for example, the heattransfer device according to any one of the first aspect to the seventhaspect may further include:

a second member including a second solid material that exhibits athermoelastic effect; and

a third heat transfer element having a third contact area that variesand that is a contact area between the third heat transfer element andthe second member, wherein

a fourth contact area that is a contact area between the second memberand the second heat transfer element varies by a variation in magnitudeof a second external force applied to the second member,

the third contact area is smaller when magnitude of the second externalforce is smaller than a second threshold being a threshold of anendothermic reaction and an exothermic reaction associated with thethermoelastic effect of the second solid material than when themagnitude of the second external force is equal to or greater than thesecond threshold, and

the fourth contact area is greater when the magnitude of the secondexternal force is smaller than the second threshold than when themagnitude of the second external force is equal to or greater than thesecond threshold.

According to the eighth aspect, the contact area between the third heattransfer element and the second member is greater when the magnitude ofthe second external force is equal to or greater than the secondthreshold than when the magnitude of the second external force issmaller than the second threshold. Therefore, heat easily transfersbetween the third heat transfer element and the second member by thermalconduction when the magnitude of the second external force is equal toor greater than the second threshold. On the other hand, the contactarea between the second heat transfer element and the second member isgreater when the magnitude of the second external force is smaller thanthe second threshold than when the magnitude of the second externalforce is equal to or greater than the second threshold. Therefore, heateasily transfers between the second heat transfer element and the secondmember by thermal conduction when the magnitude of the second externalforce is smaller than the second threshold. As described above,according to the eighth aspect, the plurality of members including thesolid materials that exhibit the thermoelastic effect and the three ormore heat transfer elements are connected in series, and temperaturedifferences between the plurality of heat transfer elements are easilyincreased.

In a ninth aspect of the present disclosure, for example, in the heattransfer device according to the eighth aspect, the third contact areamay be equal to or smaller than the fourth contact area when themagnitude of the second external force is smaller than the secondthreshold, and the third contact area may be greater than the fourthcontact area when the magnitude of the second external force is equal toor greater than the second threshold. According to the ninth aspect,heat transfer by thermal conduction is likely to be enhanced between thesecond heat transfer element and the second member when the magnitude ofthe second external force is smaller than the second threshold.Additionally, heat transfer by thermal conduction is likely to beenhanced between the third heat transfer element and the second memberwhen the magnitude of the second external force is equal to or greaterthan the second threshold.

In a tenth aspect of the present disclosure, for example, the heattransfer device according to any one of the first aspect to the seventhaspect may further include:

a second member including a second solid material that exhibits athermoelastic effect; and

a third heat transfer element having a third contact area that variesand that is a contact area between the third heat transfer element andthe second member, wherein a fourth contact area being a contact areabetween the second member and the second heat transfer element varies bya variation in magnitude of a second external force applied to thesecond member,

the third contact area is greater when the magnitude of the secondexternal force is smaller than a second threshold being a threshold ofan endothermic reaction and an exothermic reaction associated with thethermoelastic effect of the second solid material than when themagnitude of the second external force is equal to or greater than thesecond threshold, and

the fourth contact area is smaller when the magnitude of the secondexternal force is smaller than the second threshold than when themagnitude of the second external force is equal to or greater than thesecond threshold.

According to the tenth aspect, the contact area between the third heattransfer element and the second member is greater when the magnitude ofthe second external force is smaller than the second threshold than whenthe magnitude of the second external force is equal to or greater thanthe second threshold. Therefore, heat easily transfers between the thirdheat transfer element and the second member by thermal conduction whenthe magnitude of the second external force is smaller than the secondthreshold. On the other hand, the contact area between the second heattransfer element and the second member is greater when the magnitude ofthe second external force is equal to or greater than the secondthreshold than when the magnitude of the second external force issmaller than the second threshold. Therefore, heat easily transfersbetween the second heat transfer element and the second member bythermal conduction when the magnitude of the second external force isequal to or greater than the second threshold. As described above,according to the tenth aspect, the plurality of members including thesolid materials that exhibit the thermoelastic effect and the three ormore heat transfer elements can be connected in series, and temperaturedifferences between the plurality of heat transfer elements are easilyincreased.

According to an eleventh aspect of the present disclosure, for example,in the heat transfer device according to the tenth aspect, the thirdcontact area may be greater than the fourth contact area when themagnitude of the second external force is smaller than the secondthreshold, and the third contact area may be equal to or smaller thanthe fourth contact area when the magnitude of the second external forceis equal to or greater than the second threshold. According to theeleventh aspect, heat transfer by thermal conduction is likely to beenhanced between the third heat transfer element and the second memberwhen the magnitude of the second external force is smaller than thesecond threshold. Additionally, heat transfer by thermal conduction islikely to be enhanced between the second heat transfer element and thesecond member when the magnitude of the second external force is equalto or greater than the second threshold.

In a twelfth aspect of the present disclosure, for example, in the heattransfer device according to any one of the eighth aspect to theeleventh aspect, the second solid material may be in a third phase whenthe magnitude of the second external force is smaller than the secondthreshold, and the second solid material may be in a fourth phasedifferent from the third phase when the magnitude of the second externalforce is equal to or greater than the second threshold. According to thetwelfth aspect, a phase transition of the second solid material isinduced by varying the magnitude of the second external force withrespect to the second threshold, and thus the thermoelastic effect canbe exhibited.

According to a thirteenth aspect of the present disclosure, for example,in the heat transfer device according to any one of the eighth aspect tothe twelfth aspect, the second member may have a second inner perimeterand a second outer perimeter, one of the second heat transfer elementand the third heat transfer element may be disposed to face the secondinner perimeter, and the other heat transfer element may be disposed toface the second outer perimeter. According to the thirteenth aspect, thethird contact area and the fourth contact area can be adjusted byadjusting the second external force such that the second inner perimeteror the second outer perimeter of the second member is closer to thesecond heat transfer element or the third heat transfer element.

According to a fourteenth aspect of the present disclosure, in the heattransfer device according to any one of the eighth aspect to thethirteenth aspect, the second member may be a second coil spring.According to the fourteenth aspect, the third contact area and thefourth contact area can be adjusted by adjusting the second externalforce around an axis of the second coil spring.

According to a fifteenth aspect of the present disclosure, for example,in the heat transfer device according to any one of the eighth aspect tothe fourteenth aspect, a cross-section perpendicular to an axis of alinear element forming the second coil spring may include a pair ofparallel line segments defining the second inner perimeter and thesecond outer perimeter. According to the fifteenth aspect, the thirdcontact area and the fourth contact area are easily increased.

In a sixteenth aspect of the present disclosure, for example, the heattransfer device according to any one of the eighth aspect to thefifteenth aspect may further include a second drive mechanism thatcyclically increases and decreases the second external force. Accordingto the sixteenth aspect, the second external force can be cyclicallyincreased and decreased by the second drive mechanism.

Hereinafter, embodiments of the present invention will be described withreference to the drawings. It should be noted that the followingembodiments show examples, and the present disclosure is not limited bythe embodiments.

FIGS. 1 and 2 show an example of the heat transfer device of the presentdisclosure. The heat transfer device includes, for example, a main body10 a. The main body 10 a includes a first member 11, a first heattransfer element 21, and a second heat transfer element 22. The firstmember 11 includes a first solid material that exhibits thethermoelastic effect. In the first heat transfer element 21, a firstcontact area that is a contact area between the first heat transferelement 21 and the first member 11 varies. In the second heat transferelement 22, a second contact area that is a contact area between thesecond heat transfer element 22 and the first member 11 varies. In themain body 10 a, the first contact area is greater when the magnitude ofthe first external force applied to the first member 11 is smaller thana first threshold than when the magnitude of the first external force isequal to or greater than the first threshold, Therefore, heat easilytransfers between the first heat transfer element 21 and the firstmember 11 by thermal conduction when the magnitude of the first externalforce is smaller than the first threshold. On the other hand, in themain body 10 a, the second contact area is smaller when the magnitude ofthe first external force is smaller than the first threshold than whenthe magnitude of the first external force is equal to or greater thanthe first threshold. The first threshold is a threshold of anendothermic reaction and an exothermic reaction associated with thethermoelastic effect of the first solid material. Heat easily transfersbetween the second heat transfer element 22 and the first member 11 bythermal conduction when the magnitude of the first external force isequal to or greater than the first threshold. As described above, in theheat transfer device including the main body 10 a, the first contactarea and the second contact area can be varied by adjusting the firstexternal force, and the first member 11 can mediate heat transportbetween the first heat transfer element 21 and the second heat transferelement 22. Additionally, the adjustment of the first external force cancause the first solid material to exhibit the thermoelastic effect,which makes it possible to use, in the heat transfer device, heat oftransition associated with the thermoelastic effect.

In the main body 10 a, for example, the first contact area is greaterthan the second contact area when the magnitude of the first externalforce is smaller than the first threshold. Because of this, heattransfer by thermal conduction is likely to be enhanced between thefirst heat transfer element 21 and the first member 11 when themagnitude of the first external force is smaller than the firstthreshold. Additionally, in the main body 10 a, for example, the firstcontact area is equal to or smaller than the second contact area whenthe magnitude of the first external force is equal to or greater thanthe first threshold. Because of this, heat transfer by thermalconduction is likely to be enhanced between the second heat transferelement 22 and the first member 11 when the magnitude of the firstexternal force is equal to or greater than the first threshold. Itshould be noted that the first contact area does not need to be greaterthan the second contact area in an entire period when the magnitude ofthe first external force is smaller than the first threshold. Forexample, the first contact area is greater than the second contact areawhen the magnitude of the first external force is the smallest. Thefirst contact area does not need to be equal to or smaller than thesecond contact area in an entire period when the magnitude of the firstexternal force is equal to or greater than the first threshold. Forexample, the first contact area is greater than the second contact areawhen the magnitude of the first external force is the greatest.

As a result of a variation in the magnitude of the first external force,the first contact area may become zero, and the second contact area maybecome zero. In other words, depending on the magnitude of the firstexternal force, the first member 11 and the first heat transfer element21 may be completely out of contact, and the first member 11 and thesecond heat transfer element 22 may be completely out of contact.

In the main body 10 a, for example, the first solid material is in afirst phase when the magnitude of the first external force is smallerthan the first threshold, and the first solid material is in a secondphase different from the first phase when the magnitude of the firstexternal force is equal to or greater than the first threshold. A phasetransition of the first solid material is induced by varying themagnitude of the first external force with respect to the firstthreshold, and thus the thermoelastic effect can be exhibited. Thesecond phase is, for example, a phase having standard enthalpy offormation different from standard enthalpy of formation of the firstphase.

The first solid material is not limited to a particular material as longas the first solid material exhibits the thermoelastic effect. The firstsolid material may be, for example, a shape-memory alloy, athermoelastic polymer, or a plastic crystal. Examples of theshape-memory alloy include a nickel-titanium alloy, acopper-aluminum-nickel alloy, and a copper-zinc-aluminum alloy. Thethennoelastic polymer may be, for example, a block copolymer ofpolyethylene terephthalate (PET) and polyethylene oxide (PEO). Thethermoelastic polymer may be, for example, a block copolymer includingpolystyrene and poly(1,4-butadiene). The thermoelastic polymer may be,for example, an ABA triblock copolymer of poly(2-methyl-2-oxazoline) andpolytetrahydrofuran. The thermoelastic polymer may be, for example,nylon or a natural rubber. Examples of the plastic crystal includeneopentyl glycol (NPG), pentaglycerin (PG), pentaerythritol (PE),2-amino-2-methyl-1,3-propanediol (AMP), tris(hydroxymethyl)aminomethane(TRIS), 2-methyl-2-nitro-1-propanol (MNP), and2-nitro-2-methyl-1,3-propanediol (NMP).

For example, in the case where the first solid material is anickel-titanium alloy, either the first phase or the second phase is theaustenite phase and the other phase is the martensite phase. In thiscase, the first threshold is, for example, about 140 MPa. The firstthreshold may be defined as a particular value, or may be defined as aset of values between a lower limit and an upper limit greater than thelower limit.

FIG. 3 is a perspective view showing the first member 11. The firstmember 11 has, for example, a first inner perimeter 11 u and a firstouter perimeter 11 s. As shown in FIG. 2 , in the main body 10 a, forexample, the second heat transfer element 22 is disposed to face thefirst inner perimeter 11 u, and the first heat transfer element 21 isdisposed to face the first outer perimeter 11 s. The main body 10 a maybe modified such that the first heat transfer element 21 is disposed toface the first inner perimeter 11 u and the second heat transfer element22 is disposed to face the first outer perimeter 11 s, With such astructural feature, the first contact area and the second contact areacan be adjusted by adjusting the first external force such that thefirst inner perimeter 11 u or the first outer perimeter 11 s is closerto the first heat transfer element 21 or the second heat transferelement 22.

In the main body 10 a, the first heat transfer element 21 is, forexample, a ring-shaped component disposed around the first member 11.The first heat transfer element 21 is, for example, formed of a metalmaterial such as a metal or an alloy. The first heat transfer element 21may be a hollow component or a non-hollow component. When the first heattransfer element 21 is a hollow component, a liquid or powdery substancemay be charged in the first heat transfer element 21 or a fluid may flowin the first heat transfer element 21.

In the main body 10 a, the second heat transfer element 22 is, forexample, a cylindrical or tubular component, and the first member 11 isdisposed around the second heat transfer element 22. The second heattransfer element 22 is, for example, formed of a metal material such asa metal or an alloy. The second heat transfer element 22 may be a hollowcomponent or a non-hollow component. When the second heat transferelement 22 is a hollow component, a liquid or powdery substance may becharged in the second heat transfer element 22 or a fluid may flow inthe second heat transfer element 22.

In the main body 10 a, for example, the temperature of the first heattransfer element 21 is kept higher than the temperature of the secondheat transfer element 22.

As shown in FIG. 3 , the first member 11 is, for example, a first coilspring, With such a structural feature, the first contact area and thesecond contact area can be adjusted by adjusting the first externalforce such that the first coil spring 11 is twisted or untwisted. Inother words, the first contact area and the second contact area can beadjusted by adjusting the first external force around an axis of thefirst coil spring. The first member 11 may be a tubular component havinga slit extending in an axis direction of the first member 11.

As shown in FIG. 2 , in the main body 10 a, a cross-sectionperpendicular to an axis of a linear element forming the first coilspring 11 includes, for example, a pair of parallel line segmentsdefining the first inner perimeter 11 u and the first outer perimeter 11s, With such a structural feature, the first contact area and the secondcontact area are easily increased. The cross-section perpendicular tothe axis of the linear element forming the first coil spring 11 may berectangular. For example, a space is arranged between a face of thesecond heat transfer element 22 facing the first inner perimeter 11 uand a face of the first heat transfer element 21 facing the first outerperimeter 11 s, A dimension of this space in a direction perpendicularto the axis of the first coil spring 11 is greater than the distancebetween the pair of parallel line segments defining the first innerperimeter 11 u and the first outer perimeter 11 s. The first coil spring11 is disposed in this space.

As shown in FIG. 2 , the main body 10 a further includes, for example, apin 35 a, a rotating member 36, and a holding member 40 a. The rotatingmember 36 is, for example, a ring-shaped member. The rotating member 36is disposed to be adjacent to the first heat transfer element 21 in theaxis direction of the first member 11, and is disposed so as to berotatable about the axis of the first member 11. The pin 35 a isattached to the rotating member 36, and a portion of the pin 35 aprojects outside in the axis direction of the first member 11. One endof the first member 11 is fixed to the rotating member 36. The holdingmember 40 a is, for example, a ring-shaped member. The holding member 40a is disposed, for example, to be adjacent to the first heat transferelement 21 in the axis direction of the first member 11. For example,the first heat transfer element 21 is disposed between the rotatingmember 36 and the holding member 40 a in the axis direction of the firstmember 11. An end portion of the first coil spring 11 is placed insidethe holding member 40 a, and is fixed to the holding member 40 a.

As shown in FIG. 1 , for example, when the pin 35 a is at an initialposition, a large portion of the outer perimeter 11 s of the firstmember 11 is in contact with the first heat transfer element 21.Therefore, the temperature of the first member 11 rises by thermalconduction between the first member 11 and the first heat transferelement 21. At this point, the first solid material included in thefirst member 11 is in the first phase. On the other hand, a largeportion of the inner perimeter 11 u of the first member 11 is apart fromthe second heat transfer element 22. The rotating member 36 can berotated by moving the pin 35 a around the axis of the first member 11.The magnitude of the first external force applied to the first member 11can thereby be varied. For example, the rotating member 36 is rotated ina direction of an arrow A in FIG. 1 . Consequently, the first member 11deforms to wrap itself around the second heat transfer element 22.Moreover, the first external force increases as the rotating member 36rotates in the direction of the arrow A. When the first external forcebecomes equal to or greater than the first threshold by the rotation ofthe rotating member 36, transition of the first solid material from thefirst phase to the second phase occurs. When the first external forcereaches the maximum, a large portion of the inner perimeter 11 u of thefirst member 11 is in contact with the second heat transfer element 22,and a large portion of the outer perimeter 11 s of the first member 11is apart from the first heat transfer element 21. Thereafter, thetemperature of the first member 11 decreases by thermal conductionbetween the first member 11 and the second heat transfer element 22.Next, the rotating member 36 is rotated in a direction of an arrow B inFIG. 1 toward the initial position of the pin 35 a. The first externalforce becomes smaller than the first threshold by the rotation, andtransition of the first solid material from the second phase to thefirst phase occurs. Heat of transition resulting from the phasetransition from the second phase to the first phase further decreasesthe temperature of the first member 11. When the pin 35 a is broughtback to the initial position, a large portion of the outer perimeter 11s of the first member 11 comes in contact with the first heat transferelement 21. At this point, the temperature of the first member 11 startsto rise by thermal conduction between the first member 11 and the firstheat transfer element 21.

As shown in FIG. 4 , a heat transfer device 50 further includes a firstdrive mechanism 30 in addition to the main body 10 a. The first drivemechanism 30 is a mechanism that cyclically increases and decreases thefirst external force. The first contact area and the second contact areacan be varied cyclically by the first drive mechanism 30.

The first drive mechanism 30 includes, for example, a motor 31, a rod32, and a cam 33. As shown in FIG. 4 , the rod 32 is coupled to themotor 31, and the cam 33 is fixed to an end of the rod 32. The cam 33,for example, an elliptic cylindrical component and is in contact with,for example, a side of the pin 35 a. The rod 32 and the cam 33 rotateabout an axis of the rod 32 by power generated by the motor 31. Duringthe rotation, the pin 35 a slides on a side of the cam 33. Thus,rotational movement of the rotating member 36 in the direction of thearrow A in FIG. 1 and rotational movement of the rotating member 36 inthe direction of the arrow B in FIG. 1 cyclically repeat.

The heat transfer device 50 can be modified in various respects. Forexample, the heat transfer device 50 may be modified to include a mainbody 10 b shown in FIG. 6 instead of the main body 10 a. The main body10 b is configured in the same manner as the main body 10 a, unlessotherwise described. The components of the main body 10 b that are thesame as or correspond to those of the main body 10 a are denoted by thesame reference characters, and detailed descriptions of such componentsare omitted. The description given for the main body 10 a can apply tothe main body 10 b, unless there is technical inconsistency.

FIG. 7 is a cross-sectional view of the main body 10 b along a plane VIIshown in FIG. 6 . As shown in FIG. 6 and FIG. 7 , the main body 10 bfurther includes a second member 12 and a third heat transfer element 23in addition to the first member 11, the first heat transfer element 21,and the second heat transfer element 22. The second member 12 includes asecond solid material that exhibits the thermoelastic effect. In themain body 10 b, a third contact area that is a contact area between thethird heat transfer element 23 and the second member 12 varies.Additionally, a fourth contact area that is a contact area between thesecond member 12 and the second heat transfer element 22 varies by avariation in magnitude of a second external force applied to the secondmember 12. The third contact area is smaller when the magnitude of thesecond external force is smaller than a second threshold than when themagnitude of the second external force is equal to or greater than thesecond threshold. Therefore, heat easily transfers between the thirdheat transfer element 23 and the second member 12 by thermal conductionwhen the magnitude of the second external force is equal to or greaterthan the second threshold. On the other hand, the fourth contact area isgreater when the magnitude of the second external force is smaller thanthe second threshold than when the magnitude of the second externalforce is equal to or greater than the second threshold. The secondthreshold is a threshold of an endothermic reaction and an exothermicreaction associated with the thermoelastic effect of the second solidmaterial. Therefore, heat easily transfers between the second heattransfer element 22 and the second member 12 by thermal conduction whenthe magnitude of the second external force is smaller than the secondthreshold. In the main body 10 b, the first member 11, the second member12, the first heat transfer element 21, the second heat transfer element22, and the third heat transfer element 23 are connected in series. Forexample, temperature differences between the first heat transfer element21, the second heat transfer element 22, and the third heat transferelement 23 are easily increased.

In the main body 10 b, for example, the third contact area is equal toor smaller than the fourth contact area when the magnitude of the secondexternal force is smaller than the second threshold. Because of this,heat transfer by thermal conduction is likely to be enhanced between thesecond heat transfer element 22 and the second member 12 when themagnitude of the second external force is smaller than the secondthreshold. Additionally, the third contact area is greater than thefourth contact area when the magnitude of the second external force isequal to or greater than the second threshold. Because of this, heattransfer by thermal conduction is likely to be enhanced between thethird heat transfer element 23 and the second member 12 when themagnitude of the second external force is equal to or greater than thesecond threshold. It should be noted that the third contact area doesnot need to be equal to or smaller than the fourth contact area in anentire period when the magnitude of the second external force is smallerthan the second threshold. For example, the third contact area is equalto or smaller than the fourth contact area when the magnitude of thesecond external force is the smallest. The third contact area does notneed to be greater than the fourth contact area in an entire period whenthe magnitude of the second external force is equal to or greater thanthe second threshold. For example, the third contact area is greaterthan the fourth contact area when the magnitude of the second externalforce is the greatest.

As a result of a variation in the magnitude of the second externalforce, the third contact area may become zero, and the fourth contactarea may become zero. In other words, depending on the magnitude of thesecond external force, the second member 12 and the second heat transferelement 22 may be completely out of contact, and the second member 12and the third heat transfer element 23 may be completely out of contact.

In the main body 10 b, the second solid material 12 may be in a thirdphase when the magnitude of the second external force is smaller thanthe second threshold, and the second solid material 12 may be in afourth phase different from the third phase when the magnitude of thesecond external force is equal to or greater than the second threshold.With such a structural feature, a phase transition of the second solidmaterial is induced by varying the magnitude of the second externalforce with respect to the second threshold, and thus the thermoelasticeffect can be exhibited. The fourth phase is, for example, a phasehaving standard enthalpy of formation different from standard enthalpyof formation of the third phase.

The second solid material is not limited to a particular material aslong as the second solid material exhibits the thermoelastic effect.Examples of the second solid material can be the materials described asexamples of the first solid material. The second solid material may bethe same material as the first solid material or a material differentfrom the first solid material.

For example, in the case where the second solid material is anickel-titanium ahoy, either the third phase or the fourth phase is theaustenite phase and the other phase is the martensite phase. In thiscase, the second threshold is, for example, about 140 MPa. The secondthreshold may be defined as a particular value, or may be defined as aset of values between a lower limit and an upper limit greater than thelower limit.

As shown in FIG. 7 , in the main body 10 b, the second member 12 has asecond Inner perimeter 12 u and a second outer perimeter 12 s. Thesecond heat transfer element 22 may be disposed to face the second innerperimeter 12 u, and the third heat transfer element 23 may be disposedto face the second outer perimeter 12 s. The main body 10 b may bemodified such that the third heat transfer element 23 is disposed toface the second inner perimeter 12 u and the second heat transferelement 22 is disposed to face the second outer perimeter 11 s, Withsuch a structural feature, the third contact area and the fourth contactarea can be adjusted by adjusting the second external force such thatthe second inner perimeter 12 u or the second outer perimeter 12 s iscloser to the second heat transfer element 22 or the third heat transferelement 23. The second member 12 may be a tubular component having aslit extending in an axis direction of the second member 12.

As shown in FIG. 7 , the second member 12 is a second coil spring. Withsuch a structural feature, the third contact area and the fourth contactarea can be adjusted by adjusting the second external force such thatthe second coil spring 12 is twisted or untwisted. In other words, thethird contact area and the fourth contact area can be adjusted byapplying the second external force around an axis of the second coilspring.

In the main body 10 b, a cross-section perpendicular to an axis of alinear element forming the second coil spring 12 includes, for example,a pair of parallel line segments defining the second inner perimeter 12u and the second outer perimeter 12 s. With such a structural feature,the third contact area and the fourth contact area are easily increased.The cross-section perpendicular to the axis of the linear elementforming the second coil spring 12 may be rectangular. For example, aspace is arranged between a face of the second heat transfer element 22facing the second inner perimeter 12 u and a face of the third heattransfer element 23 facing the second outer perimeter 12 s. A dimensionof this space in a direction perpendicular to the axis of the secondcoil spring 12 is greater than the distance between the pair of parallelline segments defining the second inner perimeter 12 u and the secondouter perimeter 12 s. The second coil spring 12 is disposed in thisspace.

As shown in FIGS. 6 and 7 , the main body 10 b further includes, forexample, a pin 35 b, the rotating member 36, a first holding member 40b, and a second holding member 40 c. The pin 35 b is attached to therotating member 36, and a portion of the pin 35 b projects outside in adirection perpendicular to the axis of the first member 11. One end ofthe first member 11 and one end of the second member 12 are fixed to therotating member 36. Each of the first holding member 40 b and the secondholding member 40 c is, for example, a ring-shaped member. The firstholding member 40 b is disposed, for example, to be adjacent to thefirst heat transfer element 21 in the axis direction of the first member11. The second holding member 40 c is disposed, for example, to beadjacent to the third heat transfer element 23 in the axis direction ofthe second member 12. For example, the first heat transfer element 21 isdisposed between the rotating member 36 and the first holding member 40b in the axis direction of the first member 11, and the first heattransfer element 21 is disposed between the rotating member 36 and thesecond holding member 40 c in the axis direction of the second member12. An end portion of the first coil spring 11 is placed inside thefirst holding member 40 b, and is fixed to the first holding member 40b. An end portion of the second coil spring 12 is placed inside thesecond holding member 40 c, and is fixed to the second holding member 40c.

As shown in FIG. 7 , in the main body 10 b, the second heat transferelement 22 is, for example, a cylindrical or tubular component, and thefirst member 11, the second member 12, and the rotating member 36 aredisposed around the second heat transfer element 22. The second heattransfer element 22 is, for example, formed of a metal material such asa metal or an alloy. The second heat transfer element 22 may be a hollowcomponent or a non-hollow component. When the second heat transferelement 22 is a hollow component, a liquid or powdery substance may becharged in the second heat transfer element 22 or a fluid may flow inthe second heat transfer element 22.

In the main body 10 b, the third heat transfer element 23 is, forexample, a ring-shaped component disposed around the second member 12.The third heat transfer element 23 is, for example, formed of a metalmaterial such as a metal or an alloy. The third heat transfer element 23may be a hollow component or a non-hollow component. When the third heattransfer element 23 is a hollow component, a liquid or powdery substancemay be charged in the third heat transfer element 23 or a fluid may flowin the third heat transfer element 23.

In the main body 10 b, for example, the temperature of the first heattransfer element 21 is kept higher than the temperature of the secondheat transfer element 22, and the temperature of the second heattransfer element 22 is kept higher than the temperature of the thirdheat transfer element 23.

As shown in FIG. 7 , for example, when the pin 35 b is at an initialposition, a large portion of the outer perimeter 11 s of the firstmember 11 is in contact with the first heat transfer element 21,Therefore, the temperature of the first member 11 rises by thermalconduction between the first member 11 and the first heat transferelement 21. On the other hand, a large portion of the inner perimeter 12u of the second member 12 is in contact with the second heat transferelement 22. Therefore, the temperature of the second member 12 rises bythermal conduction between the second member 12 and the second heattransfer element 22. At this point, the second solid material includedin the second member 12 is in the third phase. On the other hand, alarge portion of the outer perimeter 12 s of the second member 12 isapart from the third heat transfer element 23. The rotating member 36can be rotated by moving the pin 35 b around the axis of the firstmember 11. The magnitude of the first external force applied to thefirst member 11 and the magnitude of the second external force appliedto the second member 12 can thereby be varied. When the second externalforce becomes equal to or greater than the second threshold, transitionof the second solid material from the third phase to the fourth phaseoccurs, and heat of transition resulting from the phase transition fromthe third phase to the fourth phase further increases the temperature ofthe second member 12.

Additionally, the second member 12 deforms such that the second member12 is pressed against the third heat transfer element 23, a largeportion of the outer perimeter 12 s of the second member 12 is incontact with the third heat transfer element 23, and a large portion ofthe inner perimeter 12 s of the second member 12 is apart from thesecond heat transfer element 22. Thereafter, the temperature of thesecond member 12 decreases by thermal conduction between the secondmember 12 and the third heat transfer element 23. Next, the rotatingmember 36 is rotated in the reverse direction so as to bring the pin 35b to the initial position. By the rotation, the second external forcebecomes smaller than the second threshold, and transition of the secondsolid material from the fourth phase to the third phase occurs. Heat oftransition resulting from the phase transition from the fourth phase tothe third phase further decreases the temperature of the second member12. When the pin 35 b is brought back to the initial position, a largeportion of the inner perimeter 12 u of the second member 12 comes incontact with the second heat transfer element 22 and the temperature ofthe second member 12 starts to rise by thermal conduction between thesecond member 12 and the second heat transfer element 22.

The main body 10 b may further include, for example, a second drivemechanism in addition to the first drive mechanism 30. The second drivemechanism is a mechanism that cyclically increases and decreases thesecond external force. The first drive mechanism 30 may double as thesecond drive mechanism. For example, the cam 33 of the first drivemechanism 30 is brought into contact with a side of the pin 35 b. Therod 32 and the cam 33 rotate about the axis of the rod 32 by powergenerated by the motor 31, During the rotation, the pin 35 b slides on aside of the cam 33. The second external force can thereby be cyclicallyincreased and decreased. The second drive mechanism may be a mechanismindependent of the first drive mechanism 30.

The main body 10 b may be modified into a main body 10 c shown in FIGS.8 to 10 . The main body 10 c is configured in the same manner as themain body 10 b, unless otherwise described. The components of the mainbody 10 c that are the same as or correspond to those of the main body10 b are denoted by the same reference characters, and detaileddescriptions of such components are omitted. The descriptions given forthe main bodies 10 a and 10 b can apply to the main body 10 c, unlessthere is technical inconsistency.

As shown in FIGS. 8 to 10 , the main body 10 c includes the secondmember 12 and the third heat transfer element 23 in addition to thefirst member 11, the first heat transfer element 21, and the second heattransfer element 22 as the main body 10 b does. FIGS. 9 and 10 arecross-sectional views of the main body 10 c along a plane IX shown inFIG. 8 . FIG. 9 shows a state of the main body 10 c observed when themagnitude of the first external force is smaller than the firstthreshold and the magnitude of the second external force is smaller thanthe second threshold. On the other hand, FIG. 10 shows a state of themain body 10 c observed when the magnitude of the first external forceis equal to or greater than the first threshold and the magnitude of thesecond external force is equal to or greater than the second threshold.The main body 10 c is configured so that the third contact area will begreater when the magnitude of the second external force is smaller thanthe second threshold than when the magnitude of the second externalforce is equal to or greater than the second threshold. In this case,the main body 10 c is configured so that the fourth contact area will besmaller when the magnitude of the second external force is smaller thanthe second threshold than when the magnitude of the second externalforce is equal to or greater than the second threshold.

With such a structural feature, heat easily transfers between the thirdheat transfer element 23 and the second member 12 by thermal conductionwhen the magnitude of the second external force is smaller than thesecond threshold. Additionally, heat easily transfers between the secondheat transfer element 22 and the second member 12 by thermal conductionwhen the magnitude of the second external force is equal to or greaterthan the second threshold.

The main body 10 c may also be configured as follows. For example, inthe main body 10 c, the third contact area is greater than the fourthcontact area when the magnitude of the second external force is smallerthan the second threshold. Because of this, heat transfer by thermalconduction is likely to be enhanced between the third heat transferelement 23 and the second member 12 when the magnitude of the secondexternal force is smaller than the second threshold. Additionally; thethird contact area is equal to or smaller than the fourth contact areawhen the magnitude of the second external force is equal to or greaterthan the second threshold. Heat transfer by thermal conduction is likelyto be enhanced between the second heat transfer element 22 and thesecond member 12 when the magnitude of the second external force isequal to or greater than the second threshold. It should be noted thatthe third contact area does not need to be greater than the fourthcontact area in an entire period when the magnitude of the secondexternal force is smaller than the second threshold. For example, thethird contact area is greater than the fourth contact area when themagnitude of the second external force is the smallest. The thirdcontact area does not need to be equal to or smaller than the fourthcontact area in an entire period when the magnitude of the secondexternal force is equal to or greater than the second threshold. Forexample the third contact area is equal to or smaller than the fourthcontact area when the magnitude of the second external force is thegreatest.

As shown in FIG. 9 , the main body 10 c includes a first the rotatingmember 36 a and a second rotating member 36 b. The first the rotatingmember 36 a is fixed to the first heat transfer element 21, and thesecond rotating member 36 b is fixed to the third heat transfer element23. The first heat transfer element 21 is formed, for example, into arotating body including a base and a projecting portion projecting fromthe base. The second heat transfer element 22 is formed, for example,into a rotating body including: a tubular portion having a bottom; and aprojecting portion projecting from the bottom of the tubular portion.The third heat transfer element 23 is formed into a rotating bodyincluding a tubular portion having a bottom. The axis of the first heattransfer element 21, the axis of the second heat transfer element 22,and the axis of the third heat transfer element 23 extend, for example,in alignment with each other. One end of the first member 11 is fixed tothe base of the first heat transfer element 21. The other end of thefirst member 11 is fixed to an inner face of the bottom of the tubularportion of the second heat transfer element 22. The one end of thesecond member 12 is fixed to an inner face of the bottom of the thirdheat transfer element 23. The other end of the second member 12 is fixedto an outer face of the bottom of the tubular portion of the second heattransfer element 22. The first member 11 is disposed around theprojecting portion of the first heat transfer element 21 and is placedinside the tubular portion of the first heat transfer element 21. Thesecond member 12 is disposed around the projecting portion of the secondheat transfer element 21 and is placed inside the tubular portion of thethird heat transfer element 23.

As shown in FIG. 9 , the main body 10 c further includes a heatinsulator 21 d, a heat insulator 22 d, a heat insulator 22 k, and a heatinsulator 23 k. These heat insulators have, for example, heatconductivities lower than those of the first member 11 and the secondmember 12. The heat insulator 21 d has a ring shape and covers the baseof the first heat transfer element 21 at a boundary between the base andthe projecting portion. The heat insulator 22 d has a ring shape andcovers the outer face of the bottom of the tubular portion of the secondheat transfer element 22 at a boundary between the bottom of the tubularportion and the projecting portion. The heat insulator 22 k covers theinner face of the bottom of the tubular portion of the second heattransfer element 22. The heat insulator 23 k covers the inner face ofthe bottom of the tubular portion of the third heat transfer element 23.

As shown in FIG. 8 , the main body 10 c further includes, for example, atube 15. The first member 11, the second member 12, the first heattransfer element 21, the second heat transfer element 22, and the thirdheat transfer element 23 are placed inside the tube 15. An inner face ofthe tube 15 is formed of a thermal insulation material. The thermalinsulation material has, for example, a lower heat conductivity thanthose of the first member 11 and the second member 12. An axis of thetube 15 extends, for example, in alignment with the axis of the firstheat transfer element 21, the axis of the second heat transfer element22, and the axis of the third heat transfer element 23.

For example, the first rotating member 36 a is rotated by a given drivemechanism (not shown) in a direction of an arrow A1 shown in FIG. 8 tomake the first external force greater, and the first external forcebecomes equal to or greater than the first threshold. After that, thefirst rotating member 36 a is rotated by the drive mechanism in adirection of an arrow B1 shown in FIG. 8 to make the first externalforce smaller, and the first external force becomes smaller than thefirst threshold. On the other hand, the second rotating member 36 b isrotated by a given drive mechanism (not shown) in a direction of anarrow A2 to make the second external force greater. After that, thesecond rotating member 36 b is rotated by the drive mechanism in adirection of an arrow B2 to make the second external force smaller.

In the main body 10 c, for example, the temperature of the second heattransfer element 22 is kept higher than the temperature of the firstheat transfer element 21, and the temperature of the third heat transferelement 23 is kept higher than the temperature of the second heattransfer element 22.

1. A heat transfer device comprising: a first member including a firstsolid material that exhibits a thermoelastic effect; a first heattransfer element having a first contact area that varies and that is acontact area between the first heat transfer element and the firstmember; and a second heat transfer element having a second contact areathat varies and that is a contact area between the second heat transferelement and the first member, wherein the first contact area is greaterwhen magnitude of a first external force applied to the first member issmaller than a first threshold being a threshold of an endothermicreaction and an exothermic reaction associated with the thermoelasticeffect of the first solid material than when the magnitude of the firstexternal force is equal to or greater than the first threshold, and thesecond contact area is smaller when the magnitude of the first externalforce is smaller than the first threshold than when the magnitude of thefirst external force is equal to or greater than the first threshold. 2.The heat transfer device according to claim 1, wherein the first contactarea is greater than the second contact area when the magnitude of thefirst external force is smaller than the first threshold, and the firstcontact area is equal to or smaller than the second contact area whenthe magnitude of the first external force is equal to or greater thanthe first threshold.
 3. The heat transfer device according to claim 1,wherein the first solid material is in a first phase when the magnitudeof the first external force is smaller than the first threshold, and thefirst solid material is in a second phase different from the first phasewhen the first external force is equal to or greater than the firstthreshold.
 4. The heat transfer device according to claim wherein thefirst member has a first inner perimeter and a first outer perimeter,one of the first heat transfer element and the second heat transferelement is disposed to face the first inner perimeter, and the otherheat transfer element is disposed to face the first outer perimeter. 5.The heat transfer device according to claim 4, wherein the first memberis a first coil spring.
 6. The heat transfer device according to claim5, wherein a cross-section perpendicular to an axis of a linear elementforming the first coil spring includes a pair of parallel line segmentsdefining the first inner perimeter and the first outer perimeter.
 7. Theheat transfer device according to claim 1, further comprising a firstdrive mechanism that cyclically increases and decreases the firstexternal force.
 8. The heat transfer device according to claim 1,further comprising: a second member including a second solid materialthat exhibits a thermoelastic effect; and a third heat transfer elementhaving a third contact area that varies and that is a contact areabetween the third heat transfer element and the second member, wherein afourth contact area that is a contact area between the second member andthe second heat transfer element varies by a variation in magnitude of asecond external force applied to the second member, the third contactarea is smaller when magnitude of the second external force is smallerthan a second threshold being a threshold of an endothermic reaction andan exothermic reaction associated with the thermoelastic effect of thesecond solid material than when the magnitude of the second externalforce is equal to or greater than the second threshold, and the fourthcontact area is greater when the magnitude of the second external forceis smaller than the second threshold than when the magnitude of thesecond external force is equal to or greater than the second threshold.9. The heat transfer device according to claim 8, wherein the thirdcontact area is equal to or smaller than the fourth contact area whenthe magnitude of the second external force is smaller than the secondthreshold, and the third contact area is greater than the fourth contactarea when the magnitude of the second external force is equal to orgreater than the second threshold.
 10. The heat transfer deviceaccording to to claim 1, further comprising: a second member including asecond solid material that exhibits a thermoelastic effect; and a thirdheat transfer element having a third contact area that varies and thatis a contact area between the third heat transfer element and the secondmember, wherein a fourth contact area being a contact area between thesecond member and the second heat transfer element varies by a variationin magnitude of a second external force applied to the second member,the third contact area is greater when the magnitude of the secondexternal force is smaller than a second threshold being a threshold ofan endothermic reaction and an exothermic reaction associated with thethermoelastic effect of the second solid material than when themagnitude of the second external force is equal to or greater than thesecond threshold, and the fourth contact area is smaller when themagnitude of the second external force is smaller than the secondthreshold than when the magnitude of the second external force is equalto or greater than the second threshold.
 11. The heat transfer deviceaccording to claim 10, wherein the third contact area is greater thanthe fourth contact area when the magnitude of the second external forceis smaller than the second threshold, and the third contact area isequal to or smaller than the fourth contact area when the magnitude ofthe second external force is equal to or greater than the secondthreshold.
 12. The heat transfer device according to claim 8, whereinthe second solid material is in a third phase when the magnitude of thesecond external force is smaller than the second threshold, and thesecond solid material is in a fourth phase different from the thirdphase when the second external force is equal to or greater than thesecond threshold.
 13. The heat transfer device according to claim 8,wherein the first member has a second inner perimeter and a second outerperimeter, one of the second heat transfer element and the third heattransfer element is disposed to face the first inner perimeter, and theother heat transfer element is disposed to face the second outerperimeter.
 14. The heat transfer device according to claim 8, whereinthe second member is a second coil spring.
 15. The heat transfer deviceaccording to claim 14, wherein a cross-section perpendicular to an axisof a linear element forming the second coil spring includes a pair ofparallel line segments defining the second inner perimeter and thesecond outer perimeter.
 16. The heat transfer device according to claim8, further comprising a second drive mechanism that cyclically increasesand decreases the second external force.